Experimental And Numerical Studies On The Local Damage Of Reinforced Concrete Slabs Under Close-in Explosions

Compared with distance explosions,close-in explosions are more likely to happen and will bring greater damage and more lost,which have brought serious threat to human life and property safety.In order to study the failure mechanism and response mode of the reinforced concrete slab under close-in explosion,explore effective numerical simulation ways for the development of damage assessment tools,study distribution of fragments produced by explosion and provide some suggestions for the development of antiknock specification,research was mainly carried out by the following three aspects in this article:(1)Five groups of field tests about reinforced concrete slabs under close-in explosion were conducted,the failure mode and mechanism of reinforced concrete slabs under close-in explosion were studied,the damage conditions on the rear face and front face of the slabs were analyzed and compared,the size,shape and symmetry of the holes generated in the explosions were measured,and the overall failure mode of the slabs were observed and measured.Results show that,compared with whole bending or shear failure of reinforced concrete slabs under distance explosion,the damage model of slabs under close-in explosions is significantly different.Local failure modes such as penetration and crushing damage,fragments spalling and ejection are mainly happen in close-in explosion.This is mainly because the distribution and characteristics of blast loadings acted on the reinforced concrete slabs under close-in explosion are different from distance explosion.(2)Fragments generated by explosion in the five groups were collected,screened,weighed and classified,the ejection distribution,size distribution,mass distribution,projectile velocity and shape of the fragments were studied.It found that: the total projectile interval of the fragments is fan-shaped,and the threat of fragments ejecting mainly comes from the longitudinal direction;the proportion of small-sized fragments increases with the decrease of the proportional distance,and the proportion of fragments with size range of 10~30mm is the largest;The cumulative mass fraction of fragments obeys the Weibull distribution;the mass of the fragments in the area of 2m of the slab is more than half of the total mass;the explosive caused a large number of large-size sharp fragments ejecting at high speed.(3)The failure mode and dynamic response of the reinforced concrete slab under close-in explosion were studied using finite element software LS-DYNA.Simulation model including air,explosive and reinforced concrete slab was built,accurate material model and scientific material definition were adopted,and erosion criterion was also adapted in LS-DYNA to avoid the mesh distortion.The comparison of numerical and test results of damage pattern of reinforced concrete slab demonstrates validity and reliability of numerical simulation.